Lighting usually is an integral part of an office, factory, store, supermarket, hospital, home, other building, parking lot, walkway, roadway, park or other improved location. Light fixtures most commonly are located in close proximity above or on the sides of locations that people tend to occupy. A typical building incorporates a range of fixtures to address occupants' needs. For example, a building may use 2 foot, 4 foot, or 8 foot fluorescent light fixtures with different wattages, light angles and mounting requirements. Open spaces may use fixtures of differing size and power.
Commercial buildings and other lighting typically involves the use of lighting fixtures that can only be turned on or off, such as by a mechanical switch, a motion detector, a light sensor switch or a timer. Some offices and outdoor security lighting use motion detectors with light sensors to trigger the switching of lights. If the timer is set too long, it wastes energy. If timer is set too short, it annoys its occupants. (The term “occupant” is not intended to be limited to interior building occupants but to occupants of any lighted space.) Furthermore, if an obstruction blocks a motion sensor, or if an occupant is beyond sensor range, the lighting scheme may not work at all. Occupants are often annoyed by the automatic switching off the lights when an occupant remains in a space beyond the timer period, such as by sitting still using a computer or reading a book.